CN212287422U

CN212287422U - Power tool

Info

Publication number: CN212287422U
Application number: CN201922309911.3U
Authority: CN
Inventors: M·安德鲁
Original assignee: Atlas Copco Industrial Technique AB
Current assignee: Atlas Copco Industrial Technique AB
Priority date: 2019-12-20
Filing date: 2019-12-20
Publication date: 2021-01-05
Anticipated expiration: 2029-12-20

Abstract

The present invention relates to a power tool comprising a housing and a constant velocity joint assembly (1), the constant velocity joint assembly (1) comprising an output shaft (7) and a coupling structure (5) forming a first joint configured to enable the output shaft (7) to form an angle relative to the coupling structure (5), the joint assembly (1) further comprising a crown gear (3) and a torque sensor (5f), wherein the crown gear (3) and the coupling structure (5) form a second joint configured to enable the crown gear (3) to form an angle relative to the coupling structure (5), the torque sensor (5f) being configured to detect a torque provided by the output shaft (7) and the crown gear (3) acting on the coupling structure (5), and wherein the joint assembly rotates in the housing through a bearing arrangement, the bearing arrangement is configured such that the output shaft and the crown gear are supported and rotate independently of each other relative to the housing.

Description

Power tool

Technical Field

The present invention relates generally to power tools, and more particularly to power tools including constant velocity joint assemblies.

Background

In applications requiring high power density, such as industrial assembly, advanced motor control is often required. In order to be able to accurately control the motor of a power tool, such as a nut runner, the torque is typically measured and fed back to the motor controller. A torque sensor may be used to measure torque. For example, using an angled tool, torque can be captured on the output shaft directly from the angle drive.

One drawback of the existing solutions is the risk that external factors may influence the torque measurement. For example, in use, the square drive of a nut runner may be subjected to bending forces, particularly because the user may exert a force on the tool to hold it in the correct position. This results in a bending force acting on the torque sensor that affects the torque measurement provided by the torque sensor. In addition to the bending of the output shaft, the crown gear may also bend as it is used in cooperation with the pinion driving it.

In addition, since the torque sensor is installed in the elbow, it generally requires an additional length, and therefore the length of the elbow must also be increased.

SUMMERY OF THE UTILITY MODEL

In view of the above, it is an object of the present invention to provide a design for a power tool comprising a torque sensor that solves or at least mitigates the problems of the prior art.

Thus, according to a first aspect of the present invention, there is provided a power tool comprising a housing and a constant velocity joint assembly disposed in the housing, the constant velocity joint assembly comprising: an output shaft and a coupling structure configured to drive the output shaft, wherein the output shaft and the coupling structure form a first joint configured to enable the output shaft to form an angle relative to the coupling structure at a constant rotational speed, wherein the coupling structure is provided with a torque sensor, wherein the constant velocity joint assembly further comprises a crown gear, wherein the coupling structure is configured to provide a driving connection between the crown gear and the output shaft such that the crown gear and the coupling structure form a second joint configured to enable the crown gear to form an angle relative to the coupling structure, wherein the torque sensor is configured to detect a torque provided by the output shaft and the crown gear acting on the coupling structure, wherein the joint assembly is configured to rotate in the housing by means of a bearing arrangement comprising a first set of bearing balls and a second set of bearing balls, the first set of bearing balls is configured to individually rotate the crown gear relative to the housing and the second set of bearing balls is configured to individually rotate the output shaft relative to the housing such that the output shaft and the crown gear are supported and rotate independently of each other relative to the housing.

Thus, not only the coupling structure and thereby the torque sensor is decoupled from the output shaft and from the crown gear, since bending forces acting on the crown gear and the output shaft will not be transmitted to the coupling structure and the torque sensor, since the first engagement portion and the second engagement portion can each form an angle. But furthermore, the output shaft and the crown gear are supported and rotate independently of each other relative to the housing due to a bearing arrangement by which the joint assembly is arranged in the housing. Thus, the torque sensor is effectively isolated from any bending stresses that may interfere with the torque measurement, and thus may provide a more accurate torque measurement.

The crown gear and coupling arrangement and the output shaft and coupling arrangement are coaxially arranged in a default non-rotating state, and the output shaft and crown gear are angled relative to the coupling arrangement relative to a common central axis of rotation. The output shaft may be, for example, a square drive.

According to one embodiment, the second set of balls forms part of a four-point contact ball bearing configured to solely rotate the output shaft relative to the housing. As is well known to the skilled person, a four-point bearing is a single row angular contact ball bearing having raceways designed to support axial and radial loads. More specifically, it has an array of balls with inner and outer races where the ball grooves are created from two centers, each with a radius slightly larger than the ball radius, creating four contact points. A further advantage of using such a bearing is that a particularly compact design can be achieved. In other embodiments, the second set of balls may form part of a so-called angular contact bearing.

In one embodiment, the first set of balls forms part of a second four-point contact ball bearing configured to individually rotate the crown gear relative to the housing. In another embodiment, the first set of balls forms part of a second angular contact bearing.

According to one embodiment, the inner ring of the four-point contact ball bearing is at least partially formed on the output shaft, thereby providing an advantageous compact design. According to one embodiment, the outer race of the four-point contact ball bearing is arranged to axially support the crown gear on a second opposite side remote from the second set of bearing balls, which also provides an advantageous compact design.

According to one embodiment, the outer race comprises a first portion arranged to support the crown gear on a second opposite side remote from the second set of bearing balls, and a second portion further forming a bearing shell forming part of the housing.

One embodiment includes a power and signal transmission device having a fixed portion and a rotatable portion configured to interact with the fixed portion, wherein the coupling structure has a central channel and the rotatable portion is fixedly attached to the coupling structure in the central channel and connected to the torque sensor, wherein the fixed portion is disposed in the central channel separate from the coupling structure such that the rotatable portion is rotatable relative to the fixed portion. The rotatable torque sensor can thus be supplied with power and the torque measurement signal from the torque sensor can be transmitted for further processing. According to one embodiment, the power and signal transmission means is a slip ring.

In other words, the present application provides a power tool including a housing and a constant velocity joint assembly disposed in the housing, and the constant velocity joint assembly includes: an output shaft, and a coupling structure configured to drive the output shaft, wherein the output shaft and the coupling structure form a first joint configured to enable the output shaft to form an angle relative to the coupling structure at a constant rotational speed, wherein the coupling structure is provided with a torque sensor, wherein the constant velocity joint assembly further comprises a crown gear, wherein the coupling structure is configured to provide a driving connection between the crown gear and the output shaft such that the crown gear and the coupling structure form a second joint configured to enable the crown gear to form an angle relative to the coupling structure, wherein the torque sensor is configured to detect a torque provided by the output shaft and the crown gear acting on the coupling structure, wherein the joint assembly is arranged to rotate in the housing by means of a bearing arrangement, the bearing device includes: a first set of bearing balls configured to individually rotate a crown gear relative to the housing and a second set of bearing balls configured to individually rotate an output shaft relative to the housing such that the output shaft and the crown gear are supported and rotate independently of each other relative to the housing.

The second set of bearing balls forms part of a four point contact ball bearing that rotates the output shaft solely relative to the housing.

The inner race of the four-point contact ball bearing is at least partially formed on the output shaft.

The outer race of the four-point contact ball bearing is arranged to support the crown gear on a second opposite side remote from the second set of bearing balls.

The outer race includes a first portion arranged to support the crown gear on a second, opposite side remote from the second set of bearing balls, and a second portion also forming a bearing shell that forms part of the housing.

The bearing arrangement further comprises a third set of bearing balls arranged to enable the crown gear to form an angle with respect to the coupling structure at a constant rotational speed, and a fourth set of bearing balls arranged to enable the output shaft to form an angle with respect to the coupling structure.

The torque sensor includes a strain gauge element.

The torque sensor is provided on an outer peripheral surface of the coupling structure.

The power tool comprises a power and signal transmission device having a fixed part and a rotatable part configured to interact with the fixed part, wherein the coupling structure has a central channel and the rotatable part is fixedly attached to the coupling structure in the central channel and connected to the torque sensor, wherein the fixed part is placed in the central channel and separated from the coupling structure such that the rotatable part is rotatable relative to the fixed part.

The power and signal transmission means is a slip ring.

The coupling structure has a first end provided with a first set of cup-shaped recesses for receiving a respective one of the third set of bearing balls and a second end provided with a second set of cup-shaped recesses for receiving a corresponding one of the fourth set of bearing balls.

The output shaft has a central output shaft passage provided with a third set of cup-shaped recesses for receiving a respective one of the fourth set of bearing balls, wherein the crown gear has a central crown gear passage provided with a fourth set of cup-shaped recesses for receiving a respective one of the third set of bearing balls.

The coupling structure has a first end and a second end opposite the first end, wherein the crown gear is configured to receive the first end and the output shaft is configured to receive the second end.

The first engagement means is a birfield engagement means.

Drawings

The present invention will be described in the following illustrative and non-limiting detailed description of exemplary embodiments with reference to the attached drawings, in which:

FIG. 1 schematically illustrates a side view of an exemplary power tool;

fig. 2 schematically shows a longitudinal cross-section of a bend of the power tool of fig. 1.

Detailed Description

Fig. 1 shows an example of a power tool 9 including a constant velocity joint assembly 1. The power tool 9 has an elbow 9a, and the constant velocity joint assembly 1 is disposed in the elbow 9 a.

The power tool 9 shown in fig. 1 is a hand-held power tool, more specifically a nut runner 9, but it is envisaged that other power tools may be provided with the constant velocity joint assembly 1. Fig. 2 shows a longitudinal section of the bend 9 a. The power tool 9 comprises an electric motor (not shown), a planetary gear system and a pinion 11, the pinion 11 being configured to be driven by the electric motor via the planetary gear system. The pinion 11 is configured to mesh with the gear end 3c of the crown gear 3, thereby driving the crown gear 3.

The crown gear 3 forms part of an exemplary constant velocity joint assembly 1, which constant velocity joint assembly 1 further comprises a coupling structure 5 and an output shaft 7. The crown gear wheel 3 is rotationally locked with the coupling 5 and the coupling 5 is rotationally locked with the output shaft 7. Thus, the crown gear 3 is configured to drive the coupling 5, and the coupling 5 is configured to drive the output shaft 7. In this regard, rotation of the crown gear 3 causes rotation of the output shaft 7. Furthermore, the coupling 5 and the output shaft 7 define a first engagement portion enabling the output shaft 7 to be angled relative to the coupling 5 at a constant rotational speed, and the coupling 5 and the crown gear 3 define a second engagement portion enabling the crown gear 3 to be angled relative to the coupling 5 at a constant rotational speed.

The coupling 5 has a hollow cylinder or shaft 5a, in which cylinder or shaft 5a central channel 2 is provided. The coupling structure 5 has a first end 5b and a second end 5c, each of the first and second ends 5b, 5c having a respective set of cup-shaped

grooves

5d, 5e distributed circumferentially at the respective end.

The output shaft 7 has a tool end 7a and a central output shaft channel that opens from the opposite end with respect to the tool end 7a, said central output shaft channel coaxially accommodating the second end 5c of the coupling structure 5.

Rotation of the pinion 11 thus results in rotation of the output shaft 7 via the crown gear 3 and the coupling 5. Therefore, the constant velocity joint assembly 1 can freely rotate within the power tool housing 9 b.

More specifically, the output shaft 7 and the crown gear 3 are supported and rotate independently of each other with respect to the housing. This is achieved by means of a bearing arrangement comprising a first set of bearing balls 13 and a second set of bearing balls 15, said first set of bearing balls 13 being arranged to enable rotation of the crown gear 3 alone, said second set of bearing balls 15 being arranged to enable rotation of the output shaft 7 alone, the latter set of bearing balls 15 further forming part of a four-point contact ball bearing 30, which four-point contact ball bearing 30 is arranged to enable rotation of the output shaft alone.

The four-point contact ball bearing 30 is designed such that its inner race 31 is formed on the output shaft 7.

Furthermore, the outer race 32 of the ball-supporting bearing 30 on a first side is arranged to support the crown gear 3 on a second, opposite side remote from the bearing balls 15. In the embodiment shown, the second part of the race forms a bearing shell which forms part of the housing 9.

The crown wheel 3 has a wheel end 3c provided with teeth and a central crown wheel channel 3a open from the opposite end with respect to the wheel end 3. The crown gear 3 is configured to coaxially receive a first end 5b of the coupling structure 5 in the central crown gear channel 3 a. The inner surface of the central crown wheel channel 3a is also provided with a set of cup-shaped recesses distributed in the circumferential direction. By designing the axial dimension of the coupling 5 such that the crown gear 3 and the output shaft 7 accommodate most of the length of the coupling 5, a compact design is achieved.

Furthermore, the constant velocity joint assembly 1 comprises a third set of bearing balls 4 and a fourth set of bearing balls 6. The bearing balls 4 of the first group of bearing balls are received by the cup-shaped recesses 5d of the corresponding first group of cup-shaped recesses and the cup-shaped recesses 3b of the fourth group of cup-shaped recesses. This configuration rotationally locks the crown wheel 3 and the coupling 5 and allows said crown wheel 3 to form an angle with respect to the coupling 5 when the crown wheel 3 drives the coupling, but without providing bending forces on the coupling 5.

The bearing balls 6 of the fourth group of bearing balls are received by the corresponding cup-shaped

recesses

5e and 7c of the second and third groups of cup-shaped recesses. This configuration rotationally locks the coupling 5 and the output shaft 7 and allows the output shaft 7 to be angled relative to the coupling 5 when the coupling 5 drives the output shaft 7, but does not provide a bending force on the coupling 5.

The coupling structure 5 further comprises a torque sensor 5f, which torque sensor 5f comprises a strain gauge element 5f arranged on an outer circumferential surface of the coupling structure 5, in particular the cylindrical body 5 a. The torque sensor 5f is configured to measure the torque to which the coupling structure 5 is subjected due to the stress exerted on the coupling structure 5 by the output shaft 7 and the crown gear 3.

The constant velocity joint assembly 1 further comprises a power and signal transmission device 17. The power and signal transmission means 17 is configured to supply power to the torque sensor 5f and relay a torque measurement signal from the torque sensor 5f, and the power and signal transmission means 17 includes a fixed portion 17a and a rotatable portion 17 b. The fixed portion 17a is fixedly arranged with respect to the crown gear 3, the coupling 5 and the output shaft 7 and is arranged in the central channel 2 of the coupling 5. The rotatable part 17b is rotatable relative to the fixed part and fixedly mounted to the coupling structure 5 inside the central channel 2 and is thus configured to rotate together with the coupling structure 5. The fixed part 17a is received by the rotatable part 17b such that interaction between the fixed part 17a and the rotatable part 17b provides power to the torque sensor 5f and transmits a torque measurement signal from the torque sensor 5 f. The constant velocity joint assembly 1 further includes an amplifying circuit 19, the amplifying circuit 19 being connected to the torque sensor 5f and the rotatable portion 17b, and configured to amplify the torque measurement signal generated by the torque sensor 5 f.

The power tool 9 includes an electric cord 21 and electronic equipment, such as a motor controller and a power supply unit (not shown). The electric line 21 is connected to the power and signal transmission means 17, in particular to the fixed part 17a and to the electronic devices, in order to power the torque sensor and to transmit the torque measurement signals for processing and motor control.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the present invention is not limited to the disclosed embodiments. The skilled person will appreciate that many modifications, variations and alternatives are possible within the scope defined in the appended claims. In addition, variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the articles "a" or "an" do not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims shall not be construed as limiting the scope of the claims.

Claims

1. A power tool, characterized in that the power tool comprises a housing and a constant velocity joint assembly (1) arranged in the housing, and the constant velocity joint assembly comprises:

an output shaft (7), and

a coupling structure (5) configured to drive the output shaft (7),

wherein the output shaft (7) and the coupling structure (5) form a first engagement portion configured such that the output shaft (7) is angulatable relative to the coupling structure (5) at a constant rotational speed,

wherein the coupling structure (5) is provided with a torque sensor (5f),

wherein the constant velocity joint assembly (1) further comprises a crown gear (3), wherein the coupling structure (5) is configured to provide a driving connection between the crown gear (3) and the output shaft (7) such that the crown gear (3) and the coupling structure (5) form a second joint portion configured to enable the crown gear (3) to form an angle relative to the coupling structure (5),

wherein the torque sensor (5f) is configured to detect a torque provided by the output shaft (7) and the crown gear (3) acting on the coupling structure (5),

wherein the joint assembly is arranged to rotate in the housing by means of a bearing arrangement comprising:

a first set of bearing balls (13) and a second set of bearing balls (15), the first set of bearing balls (13) configured to individually rotate a crown gear relative to the housing, the second set of bearing balls (15) configured to individually rotate an output shaft (7) relative to the housing such that the output shaft and the crown gear are supported and rotate independently of each other relative to the housing.

2. A power tool according to claim 1, characterized in that the second set of bearing balls (15) forms part of a four-point contact ball bearing (30), which four-point contact ball bearing (30) rotates the output shaft solely relative to the housing.

3. The power tool according to claim 2, characterized in that the inner race (31) of the four-point contact ball bearing is formed at least partially on the output shaft.

4. A power tool according to claim 3, characterized in that the outer race (32) of the four-point contact ball bearing is arranged to support the crown gear on a second opposite side remote from the second set of bearing balls.

5. The power tool of claim 4, wherein the outer race includes a first portion arranged to support the crown gear on a second opposing side remote from the second set of bearing balls and a second portion further forming a bearing housing forming a portion of the housing.

6. A power tool according to any one of claims 1-5, characterized in that the bearing arrangement further comprises a third set of bearing balls (4) and a fourth set of bearing balls (6), the third set of bearing balls (4) being arranged to enable the angle of the crown gear wheel (3) relative to the coupling structure (5) at a constant rotational speed, the fourth set of bearing balls (6) being arranged to enable the angle of the output shaft (7) relative to the coupling structure (5).

7. A power tool according to any one of claims 1-5, characterized in that the torque sensor (5f) comprises a strain gauge element.

8. The power tool according to claim 7, wherein the torque sensor (5f) is provided on an outer peripheral surface of the coupling structure (5).

9. A power tool according to claim 1, characterized by comprising a power and signal transmission device (17), the power and signal transmission device (17) having a fixed part (17a) and a rotatable part (17b) arranged to interact with the fixed part (17a), wherein the coupling structure (5) has a central channel (2) and the rotatable part (17b) is fixedly attached to the coupling structure (5) in the central channel (2) and connected to a torque sensor (5f), wherein the fixed part (17a) is arranged in the central channel (2) and is separate from the coupling structure (5) such that the rotatable part (17b) is rotatable relative to the fixed part (17 a).

10. A power tool according to claim 9, characterized in that the power and signal transmission means (17) is a slip ring.

11. A power tool according to claim 6, characterized in that the coupling structure (5) has a first end (5b) and a second end (5c), the first end (5b) being provided with a first set of cup-shaped recesses (5d) for accommodating a respective one of a third set of bearing balls (4), and the second end (5c) being provided with a second set of cup-shaped recesses (5e) for accommodating a corresponding one of a fourth set of bearing balls (6).

12. A power tool according to claim 11, characterized in that the output shaft (7) has a central output shaft channel provided with a third set of cup-shaped recesses (7c) for accommodating a respective one of the fourth set of bearing balls (6), wherein the crown wheel (3) has a central crown wheel channel (3a), and the central crown wheel channel (3a) is provided with a fourth set of cup-shaped recesses (3b) for accommodating a respective one of the third set of bearing balls (4).

13. The power tool according to claim 1, wherein the coupling structure (5) has a first end (5b) and a second end (5c) opposite to the first end (5b), wherein the crown gear (3) is configured to receive the first end (5b) and the output shaft (7) is configured to receive the second end (5 c).

14. A power tool according to claim 1 wherein the first engagement means is a birfield engagement means.